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The Gravitational Lensing Effect in X-ray Observations

This paper discusses the advantages of using the X-ray band for studying gravitational lensing effects. Unlike optical and radio observations, X-ray imaging provides high-resolution data that minimizes source confusion, making it easier to identify lensed quasars and galaxies. Noteworthy are Chandra's capabilities, such as its angular resolution and the ability to make mass estimates based on gas and stellar contributions. The paper also covers the lensing optical depth, magnification bias, and the relationship to the Hard X-ray Luminosity Function. Case studies in Chandra Deep Fields highlight significant findings.

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The Gravitational Lensing Effect in X-ray Observations

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  1. The Gravitational Lensing Effect in the X-ray Observation Zhenya Zheng zhengzy@mail.ustc.edu.cn

  2. Why Choose X-ray Band ? • Confusion Problem. • 1. Optical obs. : • Hard to separate stars from lensed quasars , even at high Galactic latitudes (Kochanek 1993. Castles, finding 96 lenses system until 1999) • 2. Radio obs. : ( Source structure) • Flat-spectrum radio lens surveys contain far more compact doubles than two-image lenses (e.g: JVAS, 66 of 2384 compact radio sources have multiple components within 0.3~6”, only 6 are lenses.) • Steep-spectrum surveys must cope with the enormous variety of extended radio-emission morphologies (Griffith et al. 1991)

  3. Why Choose X-ray Band ? • Confusion vanish for high-resolution X-ray imaging observation (e.g. Chandra) • 1. confusing Galactic sources are rare • 2. source structure is simple Chandra : angular resolution ~1”(on axis) covering area ~0.1 deg^2 • 3. mass estimate for clusters, from gas , stellars, and lens. Virial theory.

  4. Lenses in the X-rays, By Galaxies • Started from the Hard X-ray Luminosity Function (Ueda et al. 2003)

  5. Lensing optical depth & Magnification Bias • A Schechter Luminosity & Faber-Jackson relation • B

  6. The obs. Selection effect • Point Spread Function for Chandra • Fraction will increase with the multiple observation in one field • E.g. CDFs

  7. Searching lenses in Chandra Deep Feilds

  8. CDFS, XID 200 & XID 222 • XID200 z~ 0.75-1.38 XID 222 z~ 0.88-1.40 CL=95, photo-z (Zheng, et al 2004) Separation angle ~ 3-5” Optical image from

  9. Cluster Lensing • Very high cross section • Expected less number than galaxies. • Arclets. & effects on XRB Refregier & Loeb 1997

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